The present invention relates to a device and method for coupling skeletal muscle to a prosthetic device or bone and more specifically, a device and method for providing a mechanical linkage to actuate a prosthetic device or bone in response to skeletal muscle""s linear contraction.
An increasing number of people die annually from heart failure. The natural heart. and specifically, the cardiac muscle tissue of the natural heart (e.g., myocardium) can fail for various reasons to a point where the natural heart cannot provide sufficient circulation of blood for a body so that life can be maintained or can completely fail. Heart failure can be due to a variety of causes and/or reasons, including viral disease, idiopathic disease, valvular disease (mitral, aortic and/or both), ischemic disease, Chagas"" disease and so forth. As a solution for the dysfunctional, failing and/or diseased natural heart, attempts have been made in the past to provide a treatment and/or device to assist in or entirely maintain blood circulation.
One approach to treat a failing heart has been to transplant a heart from another human or animal into a patient. The transplant procedure requires removing an existing organ (i.e., the natural heart) for substitution with another organ (i.e., another natural heart) from another human, or potentially, from an animal. Before replacing an existing organ with another, the substitute organ must be xe2x80x9cmatchedxe2x80x9d to the recipient, which can be, at best, difficult and time consuming to accomplish. Furthermore, even if the transplanted organ matches the recipient, a risk still exists that the recipient""s body will reject the transplanted organ and attack it as a foreign object. The number of potential donor hearts is far less than the number of patients in need of a transplant. Although use of animal hearts would lessen the problem with fewer donors than recipients, there is an enhanced concern with the recipient body""s rejection of the animal heart.
Another treatment and therapy for congestive heart failure has been to wrap skeletal muscle around the epicardial surface of the patient""s own heart. Skeletal muscle can be an alternative to electromechanical systems (e.g., artificial hearts and/or ventricular assist devices), and thus may eliminate the need for an external power sources, skin penetrating power sources, or electrical induction. In a cardiomyoplasty procedure, skeletal muscle can be surgically removed from its natural anatomical position, such as across the back in the case of the latisimus dorsi muscle. Then, it is wrapped around the heart, allowed to heal, and reconditioned from a fast twitch muscle, which is susceptible to fatigue to a muscle with slow-twitch muscle fibers capable of chronic periodic contractions and that is generally fatigue resistant.
Use of a skeletal muscle wrap to power an existing natural heart has several drawbacks. Vascular interruption to the skeletal muscle while it is being removed and transplanted around the heart can lead to muscle degeneration and can adversely affect its ability to contract with sufficient force. Skeletal muscle typically requires a pre-load stretching in order to contract with sufficient force. In order to sufficiently pre-load stretch the skeletal muscle wrap, the heart has to be expanded, sometime to levels or positions that are unhealthy, or may even cause heart failure. This risk can be especially present during the end diastolic phase when the chambers of the heart are still filling with blood. Chronic overexpansion of the heart can lead to ischemic disease. Additionally, contraction of the skeletal muscle wrap is not generally sufficient if it occurs every heart beat, and greatest efficiency occurs usually with every second or third heart beat stimulation. Futhermore, a single muscle generally cannot provide sufficient contraction (e.g., pumping force) to meet full cardiac stroke requirements for the circulation of blood even for supported beats. As such, even after a skeletal wrap has been reconditioned, as mentioned above it can usually only generate enough pumping force to augment the heart""s naturally occurring pumping action and thus, usually cannot replace the pumping action of the heart.
Another approach has been to either replace the existing natural heart in a patient with an artificial heart or a ventricular assist device, or to affix a pump-like device in and/or around the existing natural heart. These circulatory assist devices must be powered by a source, which can be external to the body. External power sources are not typically restrained by size, and sometimes can be large, cumbersome, and/or bulky, which can decrease a patient""s mobility and or limit the recipient""s lifestyle choices. This can be the case even when a portable system is used for a short period of time. Some power sources, which are external to the body, power or actuate the internal device via cables, electrical cords and/or pneumatic hoses. Indefinitely having percutaneous connectors, which break or perforate through the skin, can enhance the onset of infections, even with meticulous entry site care.
A circulatory assist device can be powered by electrical power that is transmitted to the circulatory assist device using a transformer to transmit power transcutaneously through the skin. Such a power delivery system also can have drawbacks. Power to the circulatory assist device can be interrupted if for example, the coils of the transformer become displaced from each other. Also, electrical conductors can also increase the possibility of cross coupling, which can lead to power disruption because of a diversion of the magnetic flux. Drawbacks on powering and delivering power to these circulatory assist devices have generally limited use of these devices to applications having too brief a time period to, in themselves, provide a real lasting benefit to the recipient.
Others have suggested leaving skeletal muscle in situ and using it to power a circulatory assist device by delivering a force, due to unidirectional or linear shortening of the muscle""s myofibers by a linkage, such as a rod, cable, suture or cord having a plurality of bundled or braided fibers along its entire length, these transversing the muscle or its tendon. However, repeated and indefinite transmission of contractible force from muscle to an artificial device using such a linkage presents difficulties which have not been addressed previously. Due to repeated use, the suture would deliver significant pressure to the linkage/muscle interface. For example, the distribution of a muscles typical contractile force directly over half of its cross section would generate compressive stress of nearly 2000 mm of mercury (40 pounds per square inch), reducing or obliterating blood supply to the tissue. Distribution of force into a tendon, with a smaller cross section, would effect even more pressure on the tendon tissue, which already has a reduced blood supply. Chronic repetition of such high pressure may likely harm tissue integrity by causing tissue death or necrosis. Also, the suture would likely reposition itself closer to the distal end of the muscle since the muscle will likely remodel around the suture repeatedly due to the high pressure. As such, a sufficient bond between the suture and muscle to sustain muscle contract force may not develop. This failure to establish the bond and the deteriorating condition may eventually lead to the suture becoming unattached from the muscle and failing.
As can be seen, currently available treatments, procedures, and devices for coupling a prosthetic device to a muscle as a power source to maintain blood circulation have a number of shortcomings that contribute to the complexity of the procedure or device. The current devices and procedures are in limited supply, can be extremely invasive, and may only provide a benefit for a brief period of time. A need exists in the industry for an artificial coupling that can be used to harness the force and power of skeletal muscle in situ whereby an artificial circulation support device can be powered (e.g., pumped or otherwise mechanically actuated) repeatedly and indefinitely.
It is the object of the present invention to provide a device and method for coupling skeletal muscle to prosthetic device that addresses and overcomes the above-mentioned problems and shortcomings in the thoracic medicine art.
Another object of the present invention is to provide a device and method for coupling skeletal muscle to a prosthetic device or bone that minimizes muscle dissection and maximizes the linear force potential of skeletal muscle.
Yet another object of the present invention is to provide a device and method for coupling skeletal muscle to a prosthetic device or bone that leaves the skeletal muscle generally in situ.
Still another object of the present invention is to provide a device and method for coupling skeletal muscle to a prosthetic device or bone that eliminates the need for an external power supply.
It is another object of the present invention is to provide a device and method for coupling skeletal muscle to a prosthetic device or bone that can harness and utilize more than one muscle group synchronously and/or sequentially.
Yet another object of the present invention is to provide a device and method for coupling skeletal muscle to a prosthetic device that can provide a selectable contraction rate for the heart.
A further object of the present invention is to provide a device and method for coupling skeletal muscle to a prosthetic device that can provide independent control of the duration of muscle contraction and the blood ejection from the heart.
It is yet another object of the present invention is to provide a device and method for coupling skeletal muscle to a prosthetic device or bone that is durable and can repeatedly provide for the transmission of contractile force from skeletal muscle to a prosthetic device over an extended time period.
Another object of the present invention is to provide a device and method for use with a circulatory assist device that is free from an external energy source.
Still a further object of the present invention is to provide a device and method for coupling skeletal muscle to a prosthetic device that can provide for independent control of skeletal muscle pre-load and end diastolic pressure of the heart.
Additional objects, advantages, and other features of the present invention will be set forth and will become apparent to those skilled in the art upon examination of the following, or may be learned with practice of the invention.
To achieve the foregoing and other objects, and in accordance with the purpose herein, the present invention comprises a prosthetic coupling for use with skeletal muscle. The strand of the coupling includes a plurality (greater than 5,000) of continuous longitudinally extending filaments, such as polyester fiber, forming a strand. The strand has a first portion that includes a core portion wherein the filaments extend generally parallel to each other, and an exterior portion wherein the filaments are braided along its longitudinal axis around the core portion. The strand also includes a second portion wherein the filaments are generally randomly oriented and organized for integration into skeletal muscle. Preferably, the length of the filaments of the second portion is greater than about 40 mm.
A non-adhering sheath, preferably made from polyurethane, for covering a portion of the strand can also be provided. The sheath can include a tubular shaped portion for covering part or all of the first portion, and a generally frustoconically shaped portion configured for covering the terminal end or distal portion of the muscle where the second portion has been embedded.
A junctional device can be provided adjacent the end of the first portion for assisting in linking or connecting the coupling to a circulatory assist device, such as an artificial heart. An insertion kit for positioning a plurality of filaments into muscle, comprising at least one holder that configured for being attached to an end portion of the muscle, and a guide for conforming the muscle to a desired shape. Furthermore, the insertion kit may also include a frame. In the present invention, the holder may include a prosthetic strip configured for attachment to the end portion of a muscle, or alternatively, a row of teeth configured for grasping the muscle. In yet another alternative embodiment, the holder may include a clamp in which a first portion and a second portion are selectively movable between an open position arid a closed position. The clamp may also include one or more serrated surfaces, or at least one soft surface, and/or taper point penetrating pins.
The insertion kit, as mentioned above, can also include a guide. The guide can include a plurality of bars, or a plate(s). The guide also may include an attachment assembly for assisting in holding the plates against the muscle in compression. A Cushion may also be provided with the plates. Plate also may include a zone wherein a pressure differential is provided to support the muscle on the plate.
An insertion kit of the present invention may also include an inserter for inserting the plurality of filaments into the muscle. The inserter can include a first portion having plurality of slots, such as longitudinally extending slot, wherein each slot being configured to receive a needle. The slots are generally parallel to each other. The inserter may be connected to a frame along with the holder, and the guide. A frame used with the present invention can include a first and second oppositely disposed supports, and the inner surface of each support includes a longitudinally extending groove, whereby the inserter is selectively slidably along the grooves.
The inserter may also include a retainer to secure the needles in the slots.
In an alternative embodiment, the inserter may include a bar having a first portion and a second portion, and creased seam between the first and second portion. The bar may further include a plurality of slots configured for receiving the needles. The needles may even be embedded in the bar.
In yet another alternative embodiment of the present invention, the inserter can include a needle advancer operable to advance needles along the slots, such as one or more rollers, a pneumatic needle advancer, or a spring-loaded needle advancer.
Needles are preferably attached to the plurality of filaments and used to insert the filaments into the muscle. In one embodiment, the needle may include a detachable fin. Also, the needle may include at least one indentation.
In use, the muscle is generally prepared for attachment to the prosthetic coupling having filaments. The muscle can be detached from its attachment at one end, and is positioned in a tensed condition. In one embodiment, the muscle is first detached, and then the filaments are embedded therein. The filaments, preferably in a plurality of tows, of the prosthetic device are embedded in the muscle. Needles can be connected to the tows, and can be advanced into the muscle either all at once, or in a group of less than all.
The filaments of the second portion are embedded into the muscle at or adjacent one of its ends, preferably the terminal or distal end. Preferably the filaments are gathered into a plurality of tows. Each tow is swagged into or otherwise connected to a needle, and sewn into the muscle. The tows can be sewn through the muscle obliquely at least two, and preferably three times, in a S-shaped pattern. A sheath is unfolded to cover a portion of the strand, including the sites where the filaments enter the muscle, and the sites where the filaments are exposed at the surface of the muscle. The muscle covering portion of the sheath is generally diagonally corrugated to ensure against buckling as the muscle shortens and thickens with contraction.